Time-Based Offset Correction for Infrared Imaging Arrays
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Solution Overview
Problem
Mass-produced infrared cameras face challenges in correcting pixel offsets due to temperature variations, which existing methods often require accurate temperature measurements, increasing complexity and cost.
Innovation Solution
An imaging system that determines and applies offset correction values as a function of time, using flat field image data acquired at different shutter closed times to predict pixel offset drift, allowing for correction without temperature measurements, using methods like linear equations or Lagrangian interpolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature measurements are used for offset correction, then correction accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the temperature measurement component from the offset correction system, achieving accurate offset correction through time-based methods alone. By removing the temperature sensor requirement and using only time-stamped flat field data, the system achieves the desired correction accuracy without the added complexity and cost of temperature measurements.
Solution Approach 2:
The patent introduces time as an intermediary parameter to correlate offset drift with shutter closure events. Instead of directly measuring temperature, the system uses time-stamped flat field data from shutter closures to predict offset values at any given time, serving as a mediator between the shutter mechanism and the offset correction process.
2Reliability
If temperature sensors are added for offset correction, then correction reliability is improved, but manufacturing cost increases
Solution Approach 1:
The system uses its existing shutter mechanism and flat field data acquisition capability to perform offset correction without requiring external temperature sensors. The shutter closures that already occur for other operational purposes are leveraged to gather the necessary data, making the system self-sufficient and avoiding additional manufacturing costs.
Solution Approach 2:
The patent changes the correction parameter from temperature-based to time-based. By using time as the independent variable instead of temperature, the system maintains reliable offset correction while eliminating the need for temperature sensors, thereby reducing manufacturing costs.
3Measurement precision
If frequent shutter closures occur for offset correction, then correction accuracy is improved, but loss of imaging time increases
Solution Approach 1:
The patent performs offset correction predictions in advance by using time-stamped flat field data from shutter closures. The offset value function is determined beforehand and can be used to correct images taken at any subsequent time without requiring additional shutter closures, thus eliminating imaging time loss while maintaining correction precision.
Solution Approach 2:
The system dynamically adapts the shutter closure frequency based on operational needs. Rather than requiring frequent shutter closures for every image, the time-based offset value function allows the system to perform corrections asynchronously, optimizing the balance between correction accuracy and imaging time utilization.
Data Source
AI summary
A method for offset correction in an imaging system comprising acquiring image data representative of at least a portion of a frame of pixel intensity values from the detector array at two times with a shutter closed. The method includes determining an offset value function for individual pixels based on the image data acquired with the shutter closed. The method includes acquiring subsequent scene image data with the shutter open, and adjusting the scene image data relative to the flat field as predicted by the offset value function at the time the scene image data was acquired to correct for offset drift of the imaging system. In some embodiments, the imaging array is an infrared Focal Plane Array (IR FPA) in a thermal imaging camera.